1. Field of the Invention
The present invention relates to a drill pipe and casing protector, and relates more particularly to a pivotable and lockable connection arrangement used with a protector for pipe and casing strings in the bore of a well.
2. Background of the Related Art
Pipe and casing protectors are well known. Their primary purpose is to prevent a string of drill pipe in a well from contacting the well bore or casing. In the drilling of oil and gas wells, a drill bit attached to the bottom of a drill string bores a hole into an underground formation. A drill string typically comprises a long string of connected tubular drill pipe sections that extend from the surface into a well bore formed by the drill bit on the bottom of the drill string. Casing is typically installed from the surface to various depths throughout the well bore to prevent the wall of the well bore from caving in and to prevent the transfer of fluids from various drilled formations from entering the well bore. The casing also provides a channel for recovering fluids if the well is productive. The terms "casing" and "well bore" will be used interchangeably herein.
During rotary drilling operations the drill pipe is subjected to radial and axial shock and abrasion whenever the moving drill pipe comes into contact with the wall of the well bore or the casing. In many drilling operations, the drill pipe may extend underground along a curved path, such as in deviated well drilling, and in these instances a considerable amount of torque can be produced by the effects of frictional forces developed between the rotating drill pipe and the casing or the wall of the well bore. Axial drag, brought about by contact between the pipe string and bore during the upwards and downwards movement of the pipe string is also a source of shock and abrasion.
In the past, drill pipe protectors have been placed in different locations along the length of a drill pipe to keep the drill pipe and its connections away from the walls of the casing. Typically, the protector comprises a generally annular body which surrounds but is free to rotate with respect to the drill pipe. Some prior art protectors are arranged and constructed to allow them to move freely in a longitudinal direction between the tool joints at the upper and lower ends of a pipe. Alternatively, annular retaining clamps may be applied to the pipe above and below the protector to restrict its range of longitudinal movement. The clamps may be positioned so as to locate the protector at a fixed position, or may be more widely spaced to allow longitudinal movement over a predetermined length of the pipe.
The outer diameter of the protector is greater than the maximum outer diameter of the joints connecting pieces of drill pipe and less than the inside diameter of the well bore or casing. The protector is preferably designed and constructed of materials that provide a relatively low coefficient of friction between the drill pipe and the inner surface of the protector and also between the outer surface of the protector and the bore or casing. In some cases, a bushing is affixed to the pipe and provides a low friction bearing surface upon which the inner surface of the annular body reacts. A number of protectors can be fitted to the pipe string and their location and number are typically determined by the relative likelihood contact between the pipe and casing wall in a particular well. Bidirectional wells for example, because of their non-linear path are particularly susceptible to pipe and casing wall contact both during rotation and during the insertion and removal of the drill string into the well. Protectors are therefore particularly useful in these wells.
In a typical arrangement, the protector body rotates with the drill pipe in the absence of contact between the protector and the casing. However, upon frictional contact between the body and the casing, the body stops rotating, or rotates very slowly, while allowing the drill pipe to continue rotating within the body unabated. This reduces rotational drag brought about by the contact between the rotating pipe string and the casing wall. Additionally, rollers are typically set into the body to reduce axial drag caused by the pipe moving up or down against the casing wall.
Improvements to protectors in recent years have included changes to the shape and configuration of the annular body and clamps, the use of bearing members on the internal and external surfaces of the annular body and between the body and the clamps or drill pipe joints, and materials for use in the fabrication of the body and bearings. In spite of recent improvements, some problems long associated with protectors still exist. For example, the protector, with its two piece annular body must be installed around a pipe which, in most cases already has a bushing and clamps installed around its perimeter. The installation of the annular body is accomplished by connecting the two pieces together at each side or at least at one side with pins, screws and bolts or plates and relying on a some type of hinge mechanism on the opposite side. This task can require special tools and extends the time that the well is not in operation.
There is a need therefore, for a pipe and casing protector that can be quickly and easily installed with a minimum of time and parts.
There is a further need for a protector which can be installed without the use of multiple fasteners and tools.
There is yet a further need for a protector which has a simple design making it easier to use and less expensive to manufacture.